塔中区块成膜封缝堵气钻井液体系

Film-Forming Sealing and Plugging Drilling Fluid System in Tazhong Area

塔中区块奥陶系碳酸盐岩裂缝型储层气侵严重、溢流频发、循环排气时间长和井控难度大等问题长期以来阻碍了该区块的顺利钻探和高效开发,而气侵是导致诸多钻井事故的根本原因。为了有效防治和减缓气侵,通过塔中区块奥陶系储层的地质特征分析和室内砂床实验、静态承压实验、电镜扫描(SEM)实验、配伍性实验和动态污染评价实验,研制出了一套封缝堵气效果好、承压能力强的成膜封缝堵气钻井液体系,体系配方为井浆+2%～3%CY-1+3%～4%木质纤维素+3%～4%GZD,该体系的正向承压能力高达8 MPa,反向承压能力高达1 MPa,抗温性高达180℃以上,在8 MPa的驱替压力下漏失量小于10 mL。除此之外,该体系具有较好的配伍性、滤失性和流变性,为塔中区块奥陶系碳酸盐岩裂缝性储层的安全钻井提供了技术指导。

The Ordovician carbonate fractured reservoirs in Tazhong area have many serious problems, such as serious gas invasion, frequent lost circulation, long cycle time and difficult control. These problems have been hindering the processes of well drilling and reduced efficient development of the block for a long time, while the gas invasion is the most fundamental cause for the drilling accidents. In order to effectively prevent and ease the gas cut, a system of drilling fluid is developed by the analysis of geological characteristics, sand bed experiments, the static pressure test, SEM test, compatibility test and dynamic pollution evaluation experiment, which has good sealing gas ability and strong bearing ability. The analysis of experiments indicates that its thermal stability is more than 180℃ and the pressure bearing capacity could be up to 8 MPa in forward and that could be up to 1 MPa in the opposite direction. Besides, filtration is less than 10 mL under the driving pressure, 8 MPa. What is more, it has good compatibility, filtration and rheological properties. All these provide technology supports and guarantee for the security drilling of Ordovician carbonate reservoirs in Tazhong area.